Systems and methods for transmitting media content via digital radio broadcast transmission for synchronized rendering by a receiver

ABSTRACT

Systems, methods, and processor readable media are disclosed for encoding and transmitting first media content and second media content using a digital radio broadcast system, such that the second media content can be rendered in synchronization with the first media content by a digital radio broadcast receiver. The disclosed systems, methods, and processor-readable media determine when a receiver will render audio and data content that is transmitted at a given time by the digital radio broadcast transmitter, and adjust the media content accordingly to provide synchronized rendering. In exemplary embodiments, these adjustments can be provided by: 1) inserting timing instructions specifying playback time in the secondary content based on calculated delays; or 2) controlling the timing of sending the primary or secondary content to the transmitter so that it will be rendered in synchronization by the receiver.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/385,660 filed Apr. 15, 2009, the entire contents of which areincorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to digital radio broadcast transmissionand reception of media content for synchronized rendering at a digitalradio broadcast receiver.

2. Background Information

Digital radio broadcasting technology delivers digital audio and dataservices to mobile, portable, and fixed receivers. One type of digitalradio broadcasting, referred to as in-band on-channel (IBOC) digitalaudio broadcasting (DAB), uses terrestrial transmitters in the existingMedium Frequency (MF) and Very High Frequency (VHF) radio bands. HDRadio™ technology, developed by iBiquity Digital Corporation, is oneexample of an IBOC implementation for digital radio broadcasting andreception.

IBOC digital radio broadcasting signals can be transmitted in a hybridformat including an analog modulated carrier in combination with aplurality of digitally modulated carriers or in an all-digital formatwherein the analog modulated carrier is not used. Using the hybrid mode,broadcasters may continue to transmit analog AM and FM simultaneouslywith higher-quality and more robust digital signals, allowing themselvesand their listeners to convert from analog-to-digital radio whilemaintaining their current frequency allocations.

One feature of digital transmission systems is the inherent ability tosimultaneously transmit both digitized audio and data. Thus thetechnology also allows for wireless data services from AM and FM radiostations. The broadcast signals can include metadata, such as theartist, song title, or station call letters. Special messages aboutevents, traffic, and weather can also be included. For example, trafficinformation, weather forecasts, news, and sports scores can all bescrolled across a radio receiver's display while the user listens to aradio station.

IBOC digital radio broadcasting technology can provide digital qualityaudio, superior to existing analog broadcasting formats. Because eachIBOC digital radio broadcasting signal is transmitted within thespectral mask of an existing AM or FM channel allocation, it requires nonew spectral allocations. IBOC digital radio broadcasting promoteseconomy of spectrum while enabling broadcasters to supply digitalquality audio to the present base of listeners.

Multicasting, the ability to deliver several audio programs or servicesover one channel in the AM or FM spectrum, enables stations to broadcastmultiple services and supplemental programs on any of the sub-channelsof the main frequency. For example, multiple data services can includealternative music formats, local traffic, weather, news, and sports. Thesupplemental services and programs can be accessed in the same manner asthe traditional station frequency using tuning or seeking functions. Forexample, if the analog modulated signal is centered at 94.1 MHz, thesame broadcast in IBOC can include supplemental services 94.1-2, and94.1-3. Highly specialized supplemental programming can be delivered totightly targeted audiences, creating more opportunities for advertisersto integrate their brand with program content. As used herein,multicasting includes the transmission of one or more programs in asingle digital radio broadcasting channel or on a single digital radiobroadcasting signal. Multicast content can include a main programservice (MPS), supplemental program services (SPS), program service data(PSD), and/or other broadcast data.

The National Radio Systems Committee, a standard-setting organizationsponsored by the National Association of Broadcasters and the ConsumerElectronics Association, adopted an IBOC standard, designated NRSC-5, inSeptember 2005. NRSC-5 and its updates, the disclosure of which areincorporated herein by reference, set forth the requirements forbroadcasting digital audio and ancillary data over AM and FM broadcastchannels. The standard and its reference documents contain detailedexplanations of the RF/transmission subsystem and the transport andservice multiplex subsystems. Copies of the standard can be obtainedfrom the NRSC at http://www.nrscstandards.org/SG.asp. iBiquity's HDRadio technology is an implementation of the NRSC-5 IBOC standard.Further information regarding HD Radio technology can be found atwww.hdradio.com and www.ibiquity.com.

Other types of digital radio broadcasting systems include satellitesystems such as Satellite Digital Audio Radio Service (SDARS, e.g. XMRadio, Sirius), Digital Audio Radio Service (DARS, e.g., WorldSpace),and terrestrial systems such as Digital Radio Mondiale (DRM), Eureka 147(branded as DAB Digital Audio Broadcasting), DAB Version 2, and FMeXtraAs used herein, the phrase “digital radio broadcasting” encompassesdigital audio broadcasting including in-band on-channel broadcasting, aswell as other digital terrestrial broadcasting and satellitebroadcasting.

As described above, one advantage of digital radio broadcasting systemsis that they provide the capability to transmit multiple services,including audio and data, over one AM or FM frequency. For certainapplications, such as displaying album art, image slide shows, scrollingtext information, closed captioning, and product purchase information,it may be desirable to synchronize the content contained in one servicewith content contained in another service or to synchronize subservicesor components of the same service.

Conventional techniques known to the inventors for transmitting contentfor synchronized rendering by a receiver place responsibility andprocessing requirements for synchronization on the receiver. Forexample, the MPEG Transport System, which can be used to transmitsynchronized video content and audio content to be synchronized,includes a Program Clock Reference (PCR) 27 MHz clock signal in theTransport Stream for synchronization of the video and audio. Each videopacket and audio packet separately includes a Decode and PresentationTime Stamp referenced to the PCR that permit the receiver to determinewhen the packet should be decoded and rendered. As another example,Synchronized Media Integration Language v. 3.0 (SMIL) requires thereceiver to know the state of rendering primary content (e.g., how longan audio track has been playing) and provides attributes that mayspecify a begin time to render secondary content (e.g., album art) basedon the rendering of primary content, thus permitting the receiver todecode that information to provide proper synchronization. As anotherexample, SMIL also provides attributes that may specify a begin time torender secondary content at a predetermined universal coordinated time(UTC) regardless of the state of rendering the primary content.

However, the present inventors have found that none of these techniquesis entirely satisfactory for synchronizing content in the currentlydeployed HD Radio broadcast system. This system includes multiple andvarying signal processing paths on both the transmit and the receiveside that must be accounted for when synchronizing services orsubservices. In addition, Digital radio broadcast receivers typicallyinclude a baseband processor that decodes the audio content and the datacontent and outputs audio to speakers. The data is then directed to ahost controller that processes and renders the data as media content.However, the host controller typically has no knowledge of the audiosamples, including the state of playback, since the audio is sentdirectly from the baseband processor to the speakers. The presentinventors have determined that conventional synchronization approachesare not helpful for such receiver configurations and use of conventionalapproaches would require undesirable modifications at the receiver side.

SUMMARY

Embodiments of the present disclosure are directed to systems andmethods that may satisfy these needs. According to exemplaryembodiments, a computer-implemented method of encoding and transmittingfirst media content and second media content using a digital radiobroadcast system comprising a processing system, such that the secondmedia content can be rendered in synchronization with the first mediacontent by a digital radio broadcast receiver is disclosed. The methodcomprises the steps of determining at the processing system a firstvalue corresponding to a time at which a frame is to be transmitted by adigital radio broadcast transmitter; determining at the processingsystem a second value corresponding to a time at which first mediacontent transmitted in the frame is to be rendered by a digital radiobroadcast receiver based on a first latency, wherein the first latencyis based on an estimated time for processing the first media content viaa first signal path through the digital radio broadcast transmitter andthe digital radio broadcast receiver; determining at the processingsystem a third value corresponding to a time at which second mediacontent in the frame would be rendered by the digital radio broadcastreceiver based on a second latency, wherein the second latency is basedon an estimated time for processing the first media content via a secondsignal path through the digital radio broadcast transmitter and thedigital radio broadcast receiver, and wherein the second latency that isdifferent than the first latency; processing the second media content atthe processing system based on the first, second, and third values todetermine a time at which second media content is to be transmitted tothe digital radio broadcast receiver, an as to synchronize the timing ofrendering the second media content at a digital radio broadcast receiverrelative to the timing of rendering the first media content at thedigital radio broadcast receiver; and communicating to the digital radiobroadcast transmitter, the first value, first media content, secondmedia content, and data control instructions associating the secondmedia content with the first media content.

According to further exemplary embodiments, a computer-implementedmethod of encoding and transmitting first media content and second mediacontent using a digital radio broadcast system comprising a processingsystem, such that the second media content can be rendered insynchronization with the first media content by a digital radiobroadcast receiver is disclosed. The method comprises the steps ofdetermining at the processing system a first value corresponding to atime at which a frame is to be transmitted by a digital radio broadcasttransmitter; determining at the processing system a second valuecorresponding to a time at which first media content transmitted in theframe is to be rendered by a digital radio broadcast receiver based on afirst latency, wherein the first latency is based on an estimated timefor processing the first media content via a first signal path throughthe digital radio broadcast transmitter and the digital radio broadcastreceiver; determining at the processing system a third valuecorresponding to a time at which second media content in the frame wouldbe rendered by the digital radio broadcast receiver based on a secondlatency, wherein the second latency is based on an estimated time forprocessing the first media content via a second signal path through thedigital radio broadcast transmitter and the digital radio broadcastreceiver, and wherein the second latency that is different than thefirst latency; communicating the first, second, and third values to aclient; receiving second media content for the frame from the client ata time determined by the client based on the first, second, and thirdvalues, thereby controlling the timing at which second media content isto be transmitted by the digital radio broadcast transmitter, so as tosynchronize the timing of rendering the second media content at adigital radio broadcast receiver relative to the timing of rendering thefirst media content at the digital radio broadcast receiver; andcommunicating to the digital radio broadcast transmitter the firstvalue, first media content, second media content, and data controlinstructions associating the second media content with the first mediacontent.

According to further exemplary embodiments, a computer-implementedmethod of encoding and transmitting first media content and second mediacontent using a digital radio broadcast system comprising a processingsystem, such that the second media content can be rendered insynchronization with the first media content by a digital radiobroadcast receiver is disclosed. The method comprises the steps ofdetermining at the processing system a first value corresponding to atime at which a first frame is to be transmitted by a digital radiobroadcast transmitter; determining at the processing system a secondvalue corresponding to a time at which first media content transmittedin the first frame is to be rendered by a digital radio broadcastreceiver; communicating the first and second values to a client;receiving from the client second media content and timing instructionsfor the digital radio broadcast receiver to render the second mediacontent at a predetermined time in synchronization with the first mediacontent based on the first and second values; communicating a secondframe to the digital radio broadcast transmitter, wherein the secondframe includes the second media content, the timing instructions, anddata control instructions associating the first media content with thesecond media content; and communicating the first frame including thefirst media content and the first value to the digital radio broadcasttransmitter such that the first media content and the second mediacontent are rendered in synchronization by the digital radio broadcastreceiver.

According to still further exemplary embodiments, a computer-implementedmethod of receiving and rendering first media content in synchronizationwith second media content in a digital radio broadcast receiver isdisclosed. The method comprises the steps of receiving a frame havingfirst media content, second media content, and data control instructionsassociating the first media content with the second media content,wherein the second media content has been composed for rendering insynchronization with the first media content based on an estimatedlatency through a digital radio broadcast transmitter and a digitalradio broadcast receiver; processing the first media content through afirst signal path in the digital radio broadcast receiver, therebyincurring a first latency; processing the second media content through asecond signal path in the digital radio broadcast receiver, therebyincurring a second latency that is different than the first latency;associating the second media content with the first media content basedon the data control instructions; and rendering the second media contentin synchronization with the first media content, wherein the digitalradio broadcast receiver renders the first media content and the secondmedia content without making determinations about the relative renderingtiming for the second media content and the first media content.

A system comprising a processing system and a memory coupled to theprocessing system is described wherein the processing system isconfigured to carry out the above-described method. Computer programminginstructions adapted to cause a processing system to carry out theabove-described method may be embodied within any suitable article ofmanufacture such as a computer readable storage medium.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood with regard to the followingdescription, appended claims, and accompanying drawings wherein:

FIG. 1 illustrates a block diagram that provides an overview of a systemin accordance with certain embodiments;

FIG. 2 is a schematic representation of a hybrid FM IBOC waveform;

FIG. 3 is a schematic representation of an extended hybrid FM IBOCwaveform;

FIG. 4 is a schematic representation of an all-digital FM IBOC waveform;

FIG. 5 is a schematic representation of a hybrid AM IBOC waveform;

FIG. 6 is a schematic representation of an all-digital AM IBOC waveform;

FIG. 7 is a functional block diagram of an AM IBOC digital radiobroadcasting receiver in accordance with certain embodiments;

FIG. 8 is a functional block diagram of an FM IBOC digital radiobroadcasting receiver in accordance with certain embodiments;

FIGS. 9 a and 9 b are diagrams of an IBOC digital radio broadcastinglogical protocol stack from the broadcast perspective;

FIG. 10 is a diagram of an IBOC digital radio broadcasting logicalprotocol stack from the receiver perspective;

FIG. 11 is a functional block diagram of digital radio broadcasttransmitter components in accordance with certain embodiments;

FIG. 12 is an exemplary signal diagram for creating a modem frame inaccordance with certain embodiments;

FIG. 13 is an exemplary content protocol packet in accordance withcertain embodiments;

FIG. 14 is an exemplary data control service in accordance with certainembodiments;

FIG. 15 illustrates an exemplary operation of an image renderingapplication in accordance with certain embodiments;

FIGS. 16 a and 16 b illustrate an exemplary digital radio receiver vocalreducing and/or eliminating capability for radio karaoke in accordancewith certain embodiments;

FIG. 17 a illustrates an exemplary process of generating synchronizedmedia content in a digital radio broadcast transmitter system fordigital radio broadcast in accordance with certain embodiments;

FIG. 17 b illustrates an exemplary process of generating synchronizedmedia content in a digital radio broadcast transmitter system fordigital radio broadcast in accordance with certain embodiments; and

FIG. 18 illustrates an exemplary process of receiving and renderingsynchronized media content in a digital radio broadcast receiver inaccordance with certain embodiments.

DESCRIPTION

Digital radio broadcast systems as described herein can transmit mediacontent for synchronized rendering at a digital radio broadcastreceiver. To overcome the receiver intensive processing required forconventional synchronization techniques, the present inventors havedeveloped novel processing of media content at the transmitter side sothat different media content can be rendered in synchronization at thereceiver.

Exemplary Digital Radio Broadcasting System

FIGS. 1-10 and the accompanying description herein provide a generaldescription of an exemplary IBOC system, exemplary broadcastingequipment structure and operation, and exemplary receiver structure andoperation. FIGS. 11-18 and the accompanying description herein provide adetailed description of exemplary approaches for transmitting mediacontent for synchronized rendering in a digital radio broadcast systemin accordance with exemplary embodiments of the present disclosure.Whereas aspects of the disclosure are presented in the context of anexemplary IBOC system, it should be understood that the presentdisclosure is not limited to IBOC systems and that the teachings hereinare applicable to other forms of digital radio broadcasting as well.

As referred to herein, a service is any analog or digital medium forcommunicating content via radio frequency broadcast. For example, in anIBOC radio signal, the analog modulated signal, the digital main programservice, and the digital supplemental program services could all beconsidered services. Other examples of services can includeconditionally accessed programs (CAs), which are programs that require aspecific access code and can be both audio and/or data such as, forexample, a broadcast of a game, concert, or traffic update service, anddata services, such as traffic data, multimedia and other files, andservice information guides (SIGs).

Additionally, as referred to herein, media content is any substantiveinformation or creative material, including, for example, audio, video,text, image, or metadata, that is suitable for processing by aprocessing system to be rendered, displayed, played back, and/or used bya human.

Furthermore, one of ordinary skill in the art would appreciate that whatamounts to synchronization can depend on the particular implementation.As a general matter, two pieces of content are synchronized if they makesense in temporal relation to one another when rendered to a listener.For example, album art may be considered synchronized with associatedaudio if the onset of the images either leads or follows the onset ofthe audio by 3 seconds or less. For a karaoke implementation, forexample, a word of karaoke text should not follow its associated timefor singing that word but can be synchronized if it precedes the timefor singing the word by as much as a few seconds (e.g., 1 to 3 seconds).In other embodiments, content may be deemed synchronized if it isrendered, for example, within about +/−3 seconds of associated audio, orwithin about +/−one-tenth of a second of associated audio.

Referring to the drawings, FIG. 1 is a functional block diagram ofexemplary relevant components of a studio site 10, an FM transmittersite 12, and a studio transmitter link (STL) 14 that can be used tobroadcast an FM IBOC digital radio broadcasting signal. The studio siteincludes, among other things, studio automation equipment 34, anEnsemble Operations Center (EOC) 16 that includes an importer 18, anexporter 20, and an exciter auxiliary service unit (EASU) 22. An STLtransmitter 48 links the EOC with the transmitter site. The transmittersite includes an STL receiver 54, an exciter 56 that includes an exciterengine (exgine) subsystem 58, and an analog exciter 60. While in FIG. 1the exporter is resident at a radio station's studio site and theexciter is located at the transmission site, these elements may beco-located at the transmission site.

At the studio site, the studio automation equipment supplies mainprogram service (MPS) audio 42 to the EASU, MPS data 40 to the exporter,supplemental program service (SPS) audio 38 to the importer, and SPSdata 36 to the importer 18. MPS audio serves as the main audioprogramming source. In hybrid modes, it preserves the existing analogradio programming formats in both the analog and digital transmissions.MPS data or SPS data, also known as program service data (PSD), includesinformation such as music title, artist, album name, etc. Supplementalprogram service can include supplementary audio content as well asprogram service data.

The importer 18 contains hardware and software for supplying advancedapplication services (AAS). AAS can include any type of data that is notclassified as MPS, SPS, or Station Information Service (SIS). SISprovides station information, such as call sign, absolute time, positioncorrelated to GPS, etc. Examples of AAS include data services forelectronic program guides, navigation maps, real-time traffic andweather information, multimedia applications, other audio services, andother data content. The content for AAS can be supplied by serviceproviders 44, which provide service data 46 to the importer via anapplication program interface (API). The service providers may be abroadcaster located at the studio site or externally sourced third-partyproviders of services and content. The importer can establish sessionconnections between multiple service providers. The importer encodes andmultiplexes service data 46, SPS audio 38, and SPS data 36 to produceexporter link data 24, which is output to the exporter via a data link.The importer 18 also encodes a SIG, in which it typically identifies anddescribes available services. For example, the SIG may include dataidentifying the genre of the services available on the current frequency(e.g., the genre of MPS audio and any SPS audio).

The importer 18 can use a data transport mechanism, which may bereferred to herein as a radio link subsystem (RLS), to provide packetencapsulation, varying levels of quality of service (e.g., varyingdegrees of forward error correction and interleaving), and bandwidthmanagement functions. The RLS uses High-Level Data Link Control (HDLC)type framing for encapsulating the packets. HDLC is known to one ofskill in the art and is described in ISO/IEC 13239:2002 Informationtechnology—Telecommunications and information exchange betweensystems—High-level data link control (HDLC) procedures. HDLC framingincludes a beginning frame delimiter (e.g., ‘0x7E’) and an ending framedelimiter (e.g., ‘0x7E’). The RLS header includes a logical address(e.g., port number), a control field for sequence numbers and otherinformation (e.g., packet 1 of 2, 2 of 2 etc.), the payload (e.g., theindex file), and a checksum (e.g., a CRC). For bandwidth management, theimporter 18 typically assigns logical addresses (e.g. ports) to AAS databased on, for example, the number and type of services being configuredat any given studio site 10. RLS is described in more detail in U.S.Pat. No. 7,305,043, which is incorporated herein by reference in itsentirety.

Due to receiver implementation choices, RLS packets can be limited insize to about 8192 bytes, but other sizes could be used. Therefore datamay be prepared for transmission according to two primary datasegmentation modes—packet mode and byte-streaming mode—for transmittingobjects larger than the maximum packet size. In packet mode the importer18 may include a large object transfer (LOT) client (e.g. a softwareclient that executes on the same computer processing system as theimporter 18 or on a different processing system such as a remoteprocessing system) to segment a “large” object (for example, a sizeableimage file) into fragments no larger than the chosen RLS packet size. Intypical embodiments objects may range in size up to 4,294,967,295 bytes.At the transmitter, the LOT client writes packets to an RLS port forbroadcast to the receiver. At the receiver, the LOT client reads packetsfrom the RLS port of the same number. The LOT client may process dataassociated with many RLS ports (e.g., typically up to 32 ports)simultaneously, both at the receiver and the transmitter.

The LOT client operates by sending a large object in several messages,each of which is no longer than the maximum packet size. To accomplishthis, the transmitter assigns an integer called a LotID to each objectbroadcast via the LOT protocol. All messages for the same object willuse the same LotID. The choice of LotID is arbitrary except that no twoobjects being broadcast concurrently on the same RLS port may have thesame LotID. In some implementations, it may be advantageous to exhaustall possible LotID values before a value is reused.

When transmitting data over-the-air, there may be some packet loss dueto the probabilistic nature of the radio propagation environment. TheLOT client addresses this issue by allowing the transmitter to repeatthe transmission of an entire object. Once an object has been receivedcorrectly, the receiver can ignore any remaining repetitions. Allrepetitions will use the same LotID. Additionally, the transmitter mayinterleave messages for different objects on the same RLS port no longas each object on the port has been assigned a unique LotID.

The LOT client divides a large object into messages, which are furthersubdivided into fragments. Preferably all the fragments in a message,excepting the last fragment, are a fixed length such as 256 bytes. Thelast fragment may be any length that is less than the fixed length(e.g., less than 256 bytes). Fragments are numbered consecutivelystarting from zero. However, in some embodiments an object may have azero-length object—the messages would contain only descriptiveinformation about the object.

The LOT client typically uses two types of messages—a full headermessage, and a fragment header message. Each message includes a headerfollowed by fragments of the object. The full header message containsthe information to reassemble the object from the fragments plusdescriptive information about the object. By comparison, the fragmentheader message contains only the reassembly information. The LOT clientof the receiver (e.g. a software and/or hardware application thattypically executes within the data processors 232 and 288 of FIGS. 7 and8 respectively or any other suitable processing system) distinguishesbetween the two types of messages by a header-length field (e.g. fieldname “hdrLen”). Each message can contain any suitable number offragments of the object identified by the LotID in the header as long asthe maximum RLS packet length is not exceeded. There is no requirementthat all messages for an object contain the same number of fragments.Table 1 below illustrates exemplary field names and their correspondingdescriptions for a full header message. Fragment header messagestypically include only the hdrLen, repeat, LotID, and position fields.

TABLE 1 FIELD NAME DESCRIPTION hdrLen Size of the header in bytes,including the hdrLen field. Typically ranges from 24-255 bytes. RepeatNumber of object repetitions remaining. Typically ranges from 0 to 255.All messages for the same repetition of the object use the same repeatvalue. When repeating an object, the transmitter broadcasts all messageshaving repeat = R before broadcasting any messages having repeat = R− 1. A value of 0 typically means the object will not be repeated again.LotID Arbitrary identifier assigned by the transmitter to the object.Typically range from 0 to 65,535. All messages for the same object usethe same LotID value. Position The byte offset in the reassembled objectof the first fragment in the message equals 256*position. Equivalent to“fragment number”. Version Version of the LOT protocol discardTime Year,month, day, hour, and minute after which the object may be discarded atthe receiver. Expressed in Coordinated Universal Time (UTC). fileSizeTotal size of the object in bytes. mime Hash MIME hash describing thetype of object filename File name associated with the object

Full header and fragment header messages may be sent in any ratioprovided that at least one full header message is broadcast for eachobject. Bandwidth efficiency will typically be increased by minimizingthe number of full header messages; however, this may increase the timenecessary for the receiver to determine whether an object is of interestbased on the descriptive information that is only present in the fullheader. Therefore there is typically a trade between efficient use ofbroadcast bandwidth and efficient receiver processing and reception ofdesired LOT files.

In byte-streaming mode, as in packet mode, each data service isallocated a specific bandwidth by the radio station operators based onthe limits of the digital radio broadcast modem frames. The importer 18then receives data messages of arbitrary size from the data services.The data bytes received from each service are then placed in a bytebucket (e.g. a queue) and HDLC frames are constructed based on thebandwidth allocated to each service. For example, each service may haveits own HDLC frame that will be just the right size to fit into a modemframe. For example, assume that there are two data services, service #1and service #2. Service #1 has been allocated 1024 bytes, and service #2512 bytes. Now assume that service #1 sends message A having 2048 bytes,and service #2 sends message B also having 2048 bytes. Thus the firstmodem frame will contain two HDLC frames; a 1024 byte frame containing Nbytes of message A and a 512 byte HDLC frame containing M bytes ofmessage B. N & M are determined by how many HDLC escape characters areneeded and the size of the RLS header information. If no escapecharacters are needed then N=1015 and M=503 assuming a 9 byte RLSheader. If the messages contain nothing but HDLC framing bytes (i.e.0x7E) then N=503 and M=247, again assuming a 9 byte RLS headercontaining no escape characters. Also, if data service #1 does not senda new message (call it message AA) then its unused bandwidth may begiven to service #2 so its HDLC frame will be larger than its allocatedbandwidth of 512 bytes.

The exporter 20 contains the hardware and software necessary to supplythe main program service and SIS for broadcasting. The exporter acceptsdigital MPS audio 26 over an audio interface and compresses the audio.The exporter also multiplexes MPS data 40, exporter link data 24, andthe compressed digital MPS audio to produce exciter link data 52. Inaddition, the exporter accepts analog MPS audio 28 over its audiointerface and applies a pre-programmed delay to it to produce a delayedanalog MPS audio signal 30. This analog audio can be broadcast as abackup channel for hybrid IBOC digital radio broadcasts. The delaycompensates for the system delay of the digital MPS audio, allowingreceivers to blend between the digital and analog program without ashift in time. In an AM transmission system, the delayed MPS audiosignal 30 is converted by the exporter to a mono signal and sentdirectly to the STL as part of the exciter link data 52.

The EASU 22 accepts MPS audio 42 from the studio automation equipment,rate converts it to the proper system clock, and outputs two copies ofthe signal, one digital (26) and one analog (28). The EASU includes aGPS receiver that is connected to an antenna 25. The GPS receiver allowsthe EASU to derive a master clock signal, which is synchronized to theexciter's clock by use of GPS units. The EASU provides the master systemclock used by the exporter. The EASU is also used to bypass (orredirect) the analog MPS audio from being passed through the exporter inthe event the exporter has a catastrophic fault and is no longeroperational. The bypassed audio 32 can be fed directly into the STLtransmitter, eliminating a dead-air event.

STL transmitter 48 receives delayed analog MPS audio 50 and exciter linkdata 52. It outputs exciter link data and delayed analog MPS audio overSTL link 14, which may be either unidirectional or bidirectional. TheSTL link may be a digital microwave or Ethernet link, for example, andmay use the standard User Datagram Protocol or the standard TCP/IP.

The transmitter site includes an STL receiver 54, an exciter engine(exgine) 56 and an analog exciter 60. The STL receiver 54 receivesexciter link data, including audio and data signals as well as commandand control messages, over the STL link 14. The exciter link data ispassed to the exciter 56, which produces the IBOC digital radiobroadcasting waveform. The exciter includes a host processor, digitalup-converter, RE up-converter, and exgine subsystem 58. The exgineaccepts exciter link data and modulates the digital portion of the IBOCdigital radio broadcasting waveform. The digital up-converter of exciter56 converts from digital-to-analog the baseband portion of the exgineoutput. The digital-to-analog conversion is based on a GPS clock, commonto that of the exporter's GPS-based clock derived from the EASU. Thus,the exciter 56 includes a GPS unit and antenna 57. An alternative methodfor synchronizing the exporter and exciter clocks can be found in U.S.Pat. No. 7,512,175, the disclosure of which is hereby incorporated byreference. The RF up-converter of the exciter up-converts the analogsignal to the proper in-band channel frequency. The up-converted signalis then passed to the high power amplifier 62 and antenna 64 forbroadcast. In an AM transmission system, the exgine subsystem coherentlyadds the backup analog MPS audio to the digital waveform in the hybridmode; thus, the AM transmission system does not include the analogexciter 60. In addition, in an AM transmission system, the exciter 56produces phase and magnitude information and the analog signal is outputdirectly to the high power amplifier.

IBOC digital radio broadcasting signals can be transmitted in both AMand FM radio bands, using a variety of waveforms. The waveforms includean FM hybrid IBOC digital radio broadcasting waveform, an FM all-digitalIBOC digital radio broadcasting waveform, an AM hybrid IBOC digitalradio broadcasting waveform, and an AM all-digital IBOC digital radiobroadcasting waveform.

FIG. 2 is a schematic representation of a hybrid FM IBOC waveform 70.The waveform includes an analog modulated signal 72 located in thecenter of a broadcast channel 74, a first plurality of evenly spacedorthogonally frequency division multiplexed subcarriers 76 in an uppersideband 78, and a second plurality of evenly spaced orthogonallyfrequency division multiplexed subcarriers 80 in a lower sideband 82.The digitally modulated subcarriers are divided into partitions andvarious subcarriers are designated as reference subcarriers. A frequencypartition is a group of 19 OFDM subcarriers containing 18 datasubcarriers and one reference subcarrier.

The hybrid waveform includes an analog FM-modulated signal, plusdigitally modulated primary main subcarriers. The subcarriers arelocated at evenly spaced frequency locations. The subcarrier locationsare numbered from −546 to +546. In the waveform of FIG. 2, thesubcarriers are at locations +356 to +546 and −356 to −546. Each primarymain sideband is comprised of ten frequency partitions. Subcarriers 546and −546, also included in the primary main sidebands, are additionalreference subcarriers. The amplitude of each subcarrier can be scaled byan amplitude scale factor.

FIG. 3 is a schematic representation of an extended hybrid FM IBOCwaveform 90. The extended hybrid waveform is created by adding primaryextended sidebands 92, 94 to the primary main sidebands present in thehybrid waveform. One, two, or four frequency partitions can be added tothe inner edge of each primary main sideband. The extended hybridwaveform includes the analog FM signal plus digitally modulated primarymain subcarriers (subcarriers +356 to +546 and −356 to −546) and some orall primary extended subcarriers (subcarriers +280 to +355 and −280 to−355).

The upper primary extended sidebands include subcarriers 337 through 355(one frequency partition), 318 through 355 (two frequency partitions),or 280 through 355 (four frequency partitions). The lower primaryextended sidebands include subcarriers −337 through −355 (one frequencypartition), −318 through −355 (two frequency partitions), or −280through −355 (four frequency partitions). The amplitude of eachsubcarrier can be scaled by an amplitude scale factor.

FIG. 4 is a schematic representation of an all-digital FM IBOC waveform100. The all-digital waveform is constructed by disabling the analogsignal, fully extending the bandwidth of the primary digital sidebands102, 104, and adding lower-power secondary sidebands 106, 108 in thespectrum vacated by the analog signal. The all-digital waveform in theillustrated embodiment includes digitally modulated subcarriers atsubcarrier locations −546 to +546, without an analog FM signal.

In addition to the ten main frequency partitions, all four extendedfrequency partitions are present in each primary sideband of theall-digital waveform. Each secondary sideband also has ten secondarymain (SM) and four secondary extended (SX) frequency partitions. Unlikethe primary sidebands, however, the secondary main frequency partitionsare mapped nearer to the channel center with the extended frequencypartitions farther from the center.

Each secondary sideband also supports a small secondary protected (SP)region 110, 112 including 12 OFDM subcarriers and reference subcarriers279 and −279. The sidebands are referred to as “protected” because theyare located in the area of spectrum least likely to be affected byanalog or digital interference. An additional reference subcarrier isplaced at the center of the channel (0). Frequency partition ordering ofthe SP region does not apply since the SP region does not containfrequency partitions.

Each secondary main sideband spans subcarriers 1 through 190 or −1through −190. The upper secondary extended sideband includes subcarriers191 through 266, and the upper secondary protected sideband includessubcarriers 267 through 278, plus additional reference subcarrier 279.The lower secondary extended sideband includes subcarriers −191 through−266, and the lower secondary protected sideband includes subcarriers−267 through −278, plus additional reference subcarrier −279. The totalfrequency span of the entire all-digital spectrum is 396,803 Hz. Theamplitude of each subcarrier can be scaled by an amplitude scale factor.The secondary sideband amplitude scale factors can be user selectable.Any one of the four may be selected for application to the secondarysidebands.

In each of the waveforms, the digital signal is modulated usingorthogonal frequency division multiplexing (OFDM). OFDM is a parallelmodulation scheme in which the data stream modulates a large number oforthogonal subcarriers, which are transmitted simultaneously. OFDM isinherently flexible, readily allowing the mapping of logical channels todifferent groups of subcarriers.

In the hybrid waveform, the digital signal is transmitted in primarymain (PM) sidebands on either side of the analog FM signal in the hybridwaveform. The power level of each sideband is appreciably below thetotal power in the analog FM signal. The analog signal may be monophonicor stereophonic, and may include subsidiary communications authorization(SCA) channels.

In the extended hybrid waveform, the bandwidth of the hybrid sidebandscan be extended toward the analog FM signal to increase digitalcapacity. This additional spectrum, allocated to the inner edge of eachprimary main sideband, is termed the primary extended (PX) sideband.

In the all-digital waveform, the analog signal is removed and thebandwidth of the primary digital sidebands is fully extended as in theextended hybrid waveform. In addition, this waveform allows lower-powerdigital secondary sidebands to be transmitted in the spectrum vacated bythe analog FM signal.

FIG. 5 is a schematic representation of an AM hybrid IBOC digital radiobroadcasting waveform 120. The hybrid format includes the conventionalAM analog signal 122 (bandlimited to about ±5 kHz) along with a nearly30 kHz wide digital radio broadcasting signal 124. The spectrum iscontained within a channel 126 having a bandwidth of about 30 kHz. Thechannel is divided into upper 130 and lower 132 frequency bands. Theupper band extends from the center frequency of the channel to about +15kHz from the center frequency. The lower band extends from the centerfrequency to about −15 kHz from the center frequency.

The AM hybrid IBOC digital radio broadcasting signal format in oneexample comprises the analog modulated carrier signal 134 plus OFDMsubcarrier locations spanning the upper and lower bands. Coded digitalinformation representative of the audio or data signals to betransmitted (program material), is transmitted on the subcarriers. Thesymbol rate is less than the subcarrier spacing due to a guard timebetween symbols.

As shown in FIG. 5, the upper band is divided into a primary section136, a secondary section 138, and a tertiary section 144. The lower bandis divided into a primary section 140, a secondary section 142, and atertiary section 143. For the purpose of this explanation, the tertiarysections 143 and 144 can be considered to include a plurality of groupsof subcarriers labeled 146 and 152 in FIG. 5. Subcarriers within thetertiary sections that are positioned near the center of the channel arereferred to as inner subcarriers, and subcarriers within the tertiarysections that are positioned farther from the center of the channel arereferred to as outer subcarriers. The groups of subcarriers 146 and 152in the tertiary sections have substantially constant power levels. FIG.5 also shows two reference subcarriers 154 and 156 for system control,whose levels are fixed at a value that is different from the othersidebands.

The power of subcarriers in the digital sidebands is significantly belowthe total power in the analog AM signal. The level of each OFDMsubcarrier within a given primary or secondary section is fixed at aconstant value. Primary or secondary sections may be scaled relative toeach other. In addition, status and control information is transmittedon reference subcarriers located on either side of the main carrier. Aseparate logical channel, such as an IBOC Data Service (IDS) channel canbe transmitted in individual subcarriers just above and below thefrequency edges of the upper and lower secondary sidebands. The powerlevel of each primary OFDM subcarrier is fixed relative to theunmodulated main analog carrier. However, the power level of thesecondary subcarriers, logical channel subcarriers, and tertiarysubcarriers is adjustable.

Using the modulation format of FIG. 5, the analog modulated carrier andthe digitally modulated subcarriers are transmitted within the channelmask specified for standard AM broadcasting in the United States. Thehybrid system uses the analog AM signal for tuning and backup.

FIG. 6 is a schematic representation of the subcarrier assignments foran all-digital AM IBOC digital radio broadcasting waveform. Theall-digital AM IBOC digital radio broadcasting signal 160 includes firstand second groups 162 and 164 of evenly spaced subcarriers, referred toas the primary subcarriers, that are positioned in upper and lower bands166 and 168. Third and fourth groups 170 and 172 of subcarriers,referred to as secondary and tertiary subcarriers respectively, are alsopositioned in upper and lower bands 166 and 168. Two referencesubcarriers 174 and 176 of the third group lie closest to the center ofthe channel. Subcarriers 178 and 180 can be used to transmit programinformation data.

FIG. 7 is a simplified functional block diagram of the relevantcomponents of an exemplary AM IBOC digital radio broadcasting receiver200. While only certain components of the receiver 200 are shown forexemplary purposes, it should be apparent that the receiver may comprisea number of additional components and may be distributed among a numberof separate enclosures having tuners and front-ends, speakers, remotecontrols, various input/output devices, etc. The receiver 200 has atuner 206 that includes an input 202 connected to an antenna 204. Thereceiver also includes a baseband processor 201 that includes a digitaldown converter 208 for producing a baseband signal on line 210. Ananalog demodulator 212 demodulates the analog modulated portion of thebaseband signal to produce an analog audio signal on line 214. A digitaldemodulator 216 demodulates the digitally modulated portion of thebaseband signal. Then the digital signal is deinterleaved by adeinterleaver 218, and decoded by a Viterbi decoder 220. A servicedemultiplexer 222 separates main and supplemental program signals fromdata signals. A processor 224 processes the program signals to produce adigital audio signal on line 226. The analog and main digital audiosignals are blended as shown in block 228, or a supplemental digitalaudio signal is passed through, to produce an audio output on line 230.A data processor 232 processes the data signals and produces data outputsignals on lines 234, 236 and 238. The data lines 234, 236, and 238 maybe multiplexed together onto a suitable bus such as an inter-integratedcircuit (I²C), serial peripheral interface (SPI), universal asynchronousreceiver/transmitter (UART), or universal serial bus (USB). The datasignals can include, for example, SIS, NIPS data, SPS data, and one ormore AAS.

The host controller 240 receives and processes the data signals (e.g.,the SIS, MPSD, SPSD, and AAS signals). The host controller 240 comprisesa microcontroller that is coupled to the display control unit (DCU) 242and memory module 244. Any suitable microcontroller could be used suchas an Atmel® AVR 8-bit reduced instruction set computer (RISC)microcontroller, an advanced RISC machine (ARM®) 32-bit microcontrolleror any other suitable microcontroller. Additionally, a portion or all ofthe functions of the host controller 240 could be performed in abaseband processor (e.g., the processor 224 and/or data processor 232).The DCU 242 comprises any suitable I/O processor that controls thedisplay, which may be any suitable visual display such as an LCD or LEDdisplay. In certain embodiments, the DCU 242 may also control user inputcomponents via touch-screen display. In certain embodiments the hostcontroller 240 may also control user input from a keyboard, dials, knobsor other suitable inputs. The memory module 244 may include any suitabledata storage medium such as RAM, Flash ROM (e.g., an SD memory card),and/or a hard disk drive. In certain embodiments, the memory module 244may be included in an external component that communicates with the hostcontroller 240 such as a remote control.

FIG. 8 is a simplified functional block diagram of the relevantcomponents of an exemplary FM IBOC digital radio broadcasting receiver250. While only certain components of the receiver 250 are shown forexemplary purposes, it should be apparent that the receiver may comprisea number of additional components and may be distributed among a numberof separate enclosures having tuners and front-ends, speakers, remotecontrols, various input/output devices, etc. The exemplary receiverincludes a tuner 256 that has an input 252 connected to an antenna 254.The receiver also includes a baseband processor 251. The IF signal fromthe tuner 256 is provided to an analog-to-digital converter and digitaldown converter 258 to produce a baseband signal at output 260 comprisinga series of complex signal samples. The signal samples are complex inthat each sample comprises a “real” component and an “imaginary”component. An analog demodulator 262 demodulates the analog modulatedportion of the baseband signal to produce an analog audio signal on line264. The digitally modulated portion of the sampled baseband signal isnext filtered by isolation filter 266, which has a pass-band frequencyresponse comprising the collective set of subcarriers f₁-f_(n) presentin the received OFDM signal. First adjacent canceller (FAC) 268suppresses the effects of a first-adjacent interferer. Complex signal269 is routed to the input of acquisition module 296, which acquires orrecovers OFDM symbol timing offset or error and carrier frequency offsetor error from the received OFDM symbols as represented in receivedcomplex signal 298. Acquisition module 296 develops a symbol timingoffset Δt and carrier frequency offset Δf, as well as status and controlinformation. The signal is then demodulated (block 272) to demodulatethe digitally modulated portion of the baseband signal. Then the digitalsignal is deinterleaved by a deinterleaver 274, and decoded by a Viterbidecoder 276. A service demultiplexer 278 separates main and supplementalprogram signals from data signals. A processor 280 processes the mainand supplemental program signals to produce a digital audio signal online 282 and MPSD/SPSD 281. The analog and main digital audio signalsare blended as shown in block 284, or the supplemental program signal ispassed through, to produce an audio output on line 286. A data processor288 processes the data signals and produces data output signals on lines290, 292 and 294. The data lines 290, 292 and 294 may be multiplexedtogether onto a suitable bus such as an I²C, SPI, UART, or USB. The datasignals can include, for example, SIS, MPS data, SPS data, and one ormore AAS.

The host controller 296 receives and processes the data signals (e.g.,SIS, MPS data, SPS data, and AAS). The host controller 296 comprises amicrocontroller that is coupled to the DCU 298 and memory module 300.Any suitable microcontroller could be used such as an Atmel® AVR 8-bitRISC microcontroller, an advanced RISC machine (ARM®) 32-bitmicrocontroller or any other suitable microcontroller. Additionally, aportion or all of the functions of the host controller 296 could beperformed in a baseband processor (e.g., the processor 280 and/or dataprocessor 288). The DCU 298 comprises any suitable I/O processor thatcontrols the display, which may be any suitable visual display such asan LCD or LED display. In certain embodiments, the DCU 298 may alsocontrol user input components via a touch-screen display. In certainembodiments the host controller 296 may also control user input from akeyboard, dials, knobs or other suitable inputs. The memory module 300may include any suitable data storage medium such as RAM, Flash ROM(e.g., an SD memory card), and/or a hard disk drive. In certainembodiments, the memory module 300 may be included in an externalcomponent that communicates with the host controller 296 such as aremote control.

In practice, many of the signal processing functions shown in thereceivers of FIGS. 7 and 8 can be implemented using one or moreintegrated circuits. For example, while in FIGS. 7 and 8 the signalprocessing block, host controller, DCU, and memory module are shown asseparate components, the functions of two or more of these componentscould be combined in a single processor (e.g., a System on a Chip(SoC)).

FIGS. 9 a and 9 b are diagrams of an IBOC digital radio broadcastinglogical protocol stack from the transmitter perspective. From thereceiver perspective, the logical stack will be traversed in theopposite direction. Most of the data being passed between the variousentities within the protocol stack are in the form of protocol dataunits (PDUs). A PDU is a structured data block that is produced by aspecific layer (or process within a layer) of the protocol stack. ThePDUs of a given layer may encapsulate PDUs from the next higher layer ofthe stack and/or include content data and protocol control informationoriginating in the layer (or process) itself. The PDUs generated by eachlayer (or process) in the transmitter protocol stack are inputs to acorresponding layer (or process) in the receiver protocol stack.

As shown in FIGS. 9 a and 9 b, there is a configuration administrator330, which is a system function that supplies configuration and controlinformation to the various entities within the protocol stack. Theconfiguration/control information can include user defined settings, aswell as information generated from within the system such as GPS timeand position. The service interfaces 331 represent the interfaces forall services. The service interface may be different for each of thevarious types of services. For example, for MPS audio and SPS audio, theservice interface may be an audio card. For MPS data and SPS data theinterfaces may be in the form of different APIs. For all other dataservices the interface is in the form of a single API. An audio encoder332 encodes both MPS audio and SPS audio to produce core (Stream 0) andoptional enhancement (Stream 1) streams of MPS and SPS audio encodedpackets, which are passed to audio transport 333. Audio encoder 332 alsorelays unused capacity status to other parts of the system, thusallowing the inclusion of opportunistic data. MPS and SPS data isprocessed by PSD transport 334 to produce MPS and SPS data PDUs, whichare passed to audio transport 333. Audio transport 333 receives encodedaudio packets and PSD PDUs and outputs bit streams containing bothcompressed audio and program service data. The SIS transport 335receives SIS data from the configuration administrator and generates SISPDUs. A SIS PDU can contain station identification and locationinformation, indications regarding provided audio and data services, aswell as absolute time and position correlated to GPS, as well as otherinformation conveyed by the station. The AAS data transport 336 receivesAAS data from the service interface, as well as opportunistic bandwidthdata from the audio transport, and generates AAS data PDUs, which can bebased on quality of service parameters. The transport and encodingfunctions are collectively referred to as Layer 4 of the protocol stackand the corresponding transport PDUs are referred to as Layer 4 PDUs orL4 PDUs. Layer 2, which is the channel multiplex layer, (337) receivestransport PDUs from the SIS transport, AAS data transport, and audiotransport, and formats them into Layer 2 PDUs. A Layer 2 PDU includesprotocol control information and a payload, which can be audio, data, ora combination of audio and data. Layer 2 PDUs are routed through thecorrect logical channels to Layer 1 (338), wherein a logical channel isa signal path that conducts L1 PDUs through Layer 1 with a specifiedgrade of service, and possibly mapped into a predefined collection ofsubcarriers.

Layer 1 data in an IBOC system can be considered to be temporallydivided into frames (e.g., modem frames). In typical embodiments, eachmodem frame has a frame duration (T_(f)) of approximately 1.486 seconds.Each modem frame includes an absolute layer 1 frame number (ALFN) in theSIS, which is a sequential number assigned to every Layer 1 frame. ThisALFN corresponds to the broadcast starting time of a modem frame. Thestart time of ALFN 0 was 00:00:00 Universal Coordinated Time (UTC) onJan. 6, 1980 and each subsequent ALFN is incremented by one from theprevious ALFN. Thus the present time can be calculated by multiplyingthe next frame's ALFN with T_(f) and adding the total to the start timeof ALFN 0.

There are multiple Layer 1 logical channels based on service mode,wherein a service mode is a specific configuration of operatingparameters specifying throughput, performance level, and selectedlogical channels. The number of active Layer 1 logical channels and thecharacteristics defining them vary for each service mode. Statusinformation is also passed between Layer 2 and Layer 1. Layer 1 convertsthe PDUs from Layer 2 and system control information into an AM or FMIBOC digital radio broadcasting waveform for transmission. Layer 1processing can include scrambling, channel encoding, interleaving, OFDMsubcarrier mapping, and OFDM signal generation. The output of OFDMsignal generation is a complex, baseband, time domain pulse representingthe digital portion of an IBOC signal for a particular symbol. Discretesymbols are concatenated to form a continuous time domain waveform,which is modulated to create an IBOC waveform for transmission.

FIG. 10 shows a logical protocol stack from the receiver perspective. AnIBOC waveform is received by the physical layer, Layer 1 (560), whichdemodulates the signal and processes it to separate the signal intological channels. The number and kind of logical channels will depend onthe service mode, and may include logical channels P1-P4, Primary IBOCData Service Logical Channel (PIDS), S1-S5, and SIDS. Layer 1 producesL1 PDUs corresponding to the logical channels and sends the PDUs toLayer 2 (565), which demultiplexes the L1 PDUs to produce SIS PDUs, AASPDUs, and Stream 0 (core) audio PDUs and Stream 1 (optional enhanced)audio PDUs. The SIS PDUs are then processed by the SIS transport 570 toproduce SIS data, the AAS PDUs are processed by the AAS transport 575 toproduce AAS data, and the PSD PDUs are processed by the PSD transport580 to produce MPS data (MPSD) and any SPS data (SPSD). Encapsulated PSDdata may also be included in AAS PDUs, thus processed by the AAStransport processor 575 and delivered on line 577 to PSD transportprocessor 580 for further processing and producing MPSD or SPSD. The SISdata, AAS data, MPSD and SPSD are then sent to a user interface 585. TheSIS data, if requested by a user, can then be displayed. Likewise, MPSD,SPSD, and any text based or graphical AAS data can be displayed. TheStream 0 and Stream 1 PDUs are processed by Layer 4, comprised of audiotransport 590 and audio decoder 595. There may be up to N audiotransports corresponding to the number of programs received on the IBOCwaveform. Each audio transport produces encoded MPS packets or SPSpackets, corresponding to each of the received programs. Layer 4receives control information from the user interface, including commandssuch as to store or play programs, and information related to seek orscan for radio stations broadcasting an all-digital or hybrid IBOCsignal. Layer 4 also provides status information to the user interface.

The following describes an exemplary process for digital radio broadcasttransmission and reception of media content for synchronized renderingat a digital radio broadcast receiver in accordance with exemplaryembodiments. First, a general description of exemplary components andoperation of a digital radio broadcast transmitter and digital radiobroadcast receiver will be provided. Then exemplary embodiments of twotechniques for transmitting and receiving synchronized media contentwill be discussed. Finally, exemplary applications of the disclosedembodiments will be discussed. Note that in the following description,reference will be made simultaneously to components of both theexemplary AM IBOC receiver of FIG. 7 and the exemplary FM IBOC receiverof FIG. 8 since the operation of both is substantially similar forpurposes of the present disclosure. Thus, for example, the hostcontroller is referred to below as the host controller 240, 296.

An exemplary functional block diagram of the transmit-side components ofa digital radio broadcast system is illustrated in FIG. 11. As discussedabove, the functions illustrated in FIG. 11 can be performed in asuitable combination of the importer 18, the exporter 20, and a client700. These components can comprise a processing system that may includeone or more processing units that may be co-located or distributed andthat are configured (e.g., programmed with software and/or firmware) toperform the functionality described herein, wherein the processingsystem can be suitably coupled to any suitable memory (e.g., RAM, FlashROM, ROM, optical storage, magnetic storage, etc.). The importer 18communicates with a client application 700 via a request/response-typeapplication program interface (API) (i.e., the importer 18 requests datafrom the clients) to receive data content such as album art, image slideshows, scrolling text information, closed captioning, product purchaseinformation, and video. The client application 700 can be any suitableprogram that has access to the data content, such as via a database orfile directory, and that is configured to prepare and send the mediacontent to the importer 18 in response to the importer's requests.

As discussed above, the importer 18 prepares the data content andsecondary audio (if any) from a secondary audio source 702 for digitalradio broadcast transmission. It should be noted that data content fromthe client 700 travels through a first signal path in the importer 18and the secondary audio for the SPS travels through a second signal pathdifferent from the first in the importer 18. Specifically, data contentfrom the client 700 is received by an RLS encoder 704 as AAS data whereit is encapsulated as discussed above. The data content can beencapsulated using either the packet-streaming technique (e.g., LOT) orthe byte-streaming technique. Once the data content is encapsulated bythe RLS encoder 704, the RLS packets are sent to the AAS/SPS multiplexer708 where they are multiplexed with any secondary audio (e.g.,time-division multiplexed). It should be noted that data is typicallyencoded via the RLS protocol which is different than the protocol usedto transport the audio (e.g., audio transport 333 illustrated in FIG. 9b), and is therefore asynchronous with the audio. Secondary audio fromthe secondary audio source 702 is digitally encoded to producecompressed SPSA audio frames by the audio encoder 706. Any suitableaudio encoder can be used such as an HDC encoder as developed by CodingTechnologies of Dolby Laboratories, Inc., 999 Brannan Street, SanFrancisco, Calif. 94103-4938 USA; an Advanced Audio Coding (AAC)encoder; an MPEG-1 Audio Layer 3 (MP3) encoder; or a Windows Media Audio(WMA) encoder. The secondary audio source 702 may also include PSD suchas music title, artist, album name, etc., which is encoded as SPSD PDUs.The SPSD PDUs are passed from the secondary audio source 702 through theaudio encoder 706 to the RLS encoder 704. The RLS encoder thenencapsulates the SPSD PDUs and passes RLS frames back to the audioencoder 706. The audio encoder 706 combines the SPSA audio frames andthe RLS encoded SPSD (if any) into a single SPS PDU and outputs it tothe AAS/SPS multiplexer 708. The AAS/SPS multiplexer 708 then outputspackets to the exporter 20 via the importer-to-exporter (I2E) interface710.

The I2E interface 710 is a two-way handshake link that exists betweenthe importer 18 and the exporter 20 to request AAS/SPS frames for aspecific modem frame. The I2E interface is typically a TCP/IP connectionalthough it could be any other suitable type of communicationconnection. As part of the I2E interface, there is a configurable framebuffer in the exporter 20 that can be used to overcome poor networkperformance when a TCP connection is used. The I2E interface 710 outputsthe multiplexed AAS/SPS packets to the multiplexer 712 in the exporter20.

The main audio travels through a separate signal path from the secondaryaudio and the data content, and therefore incurs a delay through thedigital broadcast system that is distinct from both the data content andthe secondary audio. Specifically, the main audio content is input atthe exporter 20, while the data content and the secondary content areinput at the importer 18. The main audio is provided by the main audiosource 714, and is digitally encoded to produce compressed MPSA audioframes by the audio encoder 716. Any suitable audio encoder can be usedas described above. The main audio source 714 may also include PSD thatis encoded as MPSD PDUs. The MPSD PDUs are passed from the audio encoder716 to the RLS encoder 718, where they are encapsulated and sent back tothe audio encoder 716 as RLS frames. The MPSD and MPSA packets arecombined into a single MPS PDU and then sent to the multiplexer 712. ASIS module generates the SIS information, including calculating thecurrent ALFN, and sends the SIS PDUs to the multiplexer 712. Themultiplexer 712 multiplexes the MPS, SPS, AAS, and SIS to form a modemframe. The multiplexer 712 then outputs the modem frame via the STL link14 (described with reference to FIG. 1 above) to the exciter 56, whichproduces the IBOC digital radio broadcasting waveform.

As noted above, the AAS, SPS and MPS may all travel through differentsignal paths in the digital radio broadcast transmission system therebyincurring different delays. The AAS incurs typically fixed delays due toRLS encoding and multiplexing in the importer 18. The SPS incurs notonly the delays for encoding (which is different than the RLS encodingdelay for data as previously discussed) and multiplexing, but alsoanother typically fixed delay for audio encoding in the importer 18. Thedelay for the SPS typically requires approximately six (6) modem framesof buffering to account for processing time. Furthermore, the SPS andAAS both incur an additional configurable delay through the I2E linkthat is typically on the order of 20 modem frames. As noted above, theMPS signal path does not pass through the I2E link and typicallyrequires only approximately one (1) modem frame of buffering to accountfor processing time in the exporter 20. In addition, the portion of thedigital radio broadcast transmitter downstream of the exporter 20typically incurs an additional two (2) modem frames of delay due tobuffering and processing. While approximate delay times have beenprovided for exemplary purposes, it should be apparent that theseexamples in no way limit the scope of this disclosure or the claims.

Similarly, the MPS and SPS audio and the AAS may travel throughdifferent signal paths in the digital radio broadcast receiver.Specifically, as discussed with reference to FIGS. 7 and 8, the MPS andSPS are decoded and output directly from the baseband processor 201, 251to the audio output 230, 286, whereas the AAS is transmitted as datacontent to the host controller 240, 296, from which it can be renderedvia the display control unit 242, 298. The digital radio broadcastreceiver typically incurs an approximately two (2) modem frames of delaydue to buffering and processing.

While it has been noted that the delays will typically vary from oneservice to another, it should also be noted that these different delayswill also vary from one radio frequency to another, and from onegeographic location to another. For example, since different radiostations may employ different hardware, software and/or configurations,the delays through the systems due to processing and buffering will notbe the same.

As a result of these varying delays due to the multiple signal paths,audio and data content can incur different latencies through the digitalradio broadcast system. The digital radio broadcast transmitter accountsfor these different latencies so as to render audio and data content insynchronization at the digital radio broadcast receiver. The importer 18includes a delay determination module 722 that calculates approximatevalues for the various delays of data and audio through the signal pathsin the digital radio broadcast system and outputs these values to theclient 700. The delay determination module 722 can be implemented inhardware, software, or any suitable combination thereof. To determinethe audio latency, the delay determination module 722 adds the variousdelays including the I2E delay, the audio buffering delay, and thetransmit/receive delays. Similarly, to determine the data content delay,the delay determination module 722 adds the various delays including theI2E delay, the data buffering delay, and the transmit/receive delays. Inexemplary embodiments, the delay determination module 722 receives thecurrent ALFN (T_(C)) (i.e., the ALFN for the modem frame currently beinggenerated by the exporter 20) from the SIS module 720. The latencyvalues can then be used to calculate a time at which the audio or datacontent delivered to the importer 18 is to be rendered at the digitalradio broadcast receiver by adding T_(C) to the calculated latency. Thetimes can be expressed, for example, in terms of ALFNs or fractionsthereof, or in terms of units of time such as seconds, milliseconds,etc. An exemplary calculation of the time at which audio or data is tobe rendered at a digital radio broadcast receiver expressed in terms ofALFNs could be:Audio ALFN(T _(A))ALFN=I2E Delay(ALFNs)+Audio Buffering(ALFNs)+Tx/RxProcessing(ALFNs)+T _(C), andData ALFN(T _(D))=I2E Delay(ALFNs)+Data Buffering(ALFNs)+Tx/RxProcessing(ALFNs)+T _(C)

It should be noted that T_(D), i.e., the time at which data content thatis delivered to the importer 18 is to be rendered by the digital radiobroadcast receiver, is typically available only if the data is beingtransmitted via byte-streaming mode as discussed above. Typically,packet delivery times cannot be predicted because the importer 18 doesnot know whether any individual packet of data will be transmitted in agiven modem frame.

The delay determination module 722 sends the T_(C), T_(A), and T_(D) (ifavailable) to the client application 700. Given these values the clientapplication 700 can apply the proper timing either in the delivery ofthe data content to the importer 18 or in the packaging of the datacontent with timing instructions such that satisfactory timesynchronization can be achieved at the receiver as discussed in moredetail below.

FIG. 12 illustrates an exemplary sequence of generating a modem frame inthe digital radio broadcast transmitter. Initially, the exporter 20sends a request message 740 to the importer 18 via the I2E interfacethat includes the current ALFN (N). This request message 740 notifiesthe importer 18 that the exporter is generating a modem frame identifiedby N and requests content for a logical channel. While described forexemplary purposes in terms of a single logical channel, it should bereadily apparent that the same process could apply to multiple logicalchannels generated for the current modem frame. The importer 18generates a content request message 742 for the client 700 that includesN, the audio ALFN, and the data ALFN (if any), which are determined asdiscussed above. In response, the client 700 retrieves and sends datacontent 744 to the importer 18. As discussed above, the client 700applies the proper timing either in the delivery of the data content tothe importer 18 or in the packaging of the data content with timinginstructions such that satisfactory time synchronization can be achievedat the receiver. The importer 18 generates data for a logical channelbased on the content from the client 700 and transmits this data 746 tothe exporter 20 via the I2E interface. The exporter 20 then generatesand delivers modem frame N 748 to the exciter 56 via the STL link 14 fordigital radio broadcast transmission 750. This process occurs within onemodem frame time and is repeated for each modem frame. Thus modem frameN+1 also shown in FIG. 12 is generated and transmitted in the samemanner.

In exemplary embodiments the client 700 adds a header to the datacontent to facilitate transport and decoding. FIG. 13 illustrates a datacontent packet in accordance with an exemplary content protocol. Thepacket includes an ordered collection of the following three items: aheader core 760, a header extension 762, and a body 764. The header core760 includes information regarding the size and the content of thepayload to enable a digital radio broadcast receiver to determinewhether it has system resources to decode and render the content. Theheader extension 762 includes information that supports the handling orrendering of the included content. And the body 764 carries the payload,where the structure and content of the data in the payload is describedin the header core 760 and the header extension 762.

The exemplary header core 760 is 8 bytes in length. While exemplarylengths are used herein for illustrative purposes, any suitable lengthsmay be used as would be readily apparent to one of ordinary skill in theart. The header core 760 includes a number of fields. First, there is aSYNC field, which is a two-byte ASCII sequence that identifies the startof the packet. These SYNC bytes can be used by the digital radiobroadcast receiver to defragment the packets when byte-streaming mode isused. Second, there is a one-byte PR field that describes the majorrevision (MAJ) and the minor revision (MIN) of the current protocolbeing used. This can be desirable to ensure that the receiver iscompatible with the protocol being used to encode the data content.Third, there is a one-byte Header EXT LEN field that describes thelength of the extension header in bytes. Fourth, there is a two-byteBody LEN field that describes the length of the body 764 in bytes. Incertain embodiments, a Body LEN of zero could indicate that the bodylength is greater than 2^16 (65536) bytes and that there is a headerextension parameter describing the actual body length. Fifth, there is aone-byte Type field that indicates the type of data included in the body764. Finally, there is a one-byte Format field that indicates the formatof the data included in the body 764. Exemplary Type and Format valuesare shown in Table 2 below.

TABLE 2 Type Value Type Interpretation Format Value FormatInterpretation 0x0 PSD 0x0 XML 0x1 ID3 0x1 Audio 0x0 Uncompressed PCMsamples 0x1 HDC 0x2 Image 0x0 JPEG 0x1 PNG 0x2 GIF 0x3 Text 0x0 ISO/IEC8859-1:1998 0x4 ISO/IEC 10646-1:2000 0xff Other N/A Application specific

As illustrated in Table 2, the data content in the packets can includeXML, tags (for example as described in the ID3 informal standard version2.3.0 available at http://www.id3.org), uncompressed pulse codemodulated (PCM) audio samples, HDC encoded audio, JPEG images, PNGimages, GIF images, ISO/IEC 8859-1:1998 encoded text, ISO/IEC10646-1:2000 encoded text, or a form of data that is applicationspecific. While these data formats are shown for exemplary purposes,these examples in no way limit the scope of the disclosure or the claimsand any other form of data could be included as would be known to one ofordinary skill in the art such as, for example, MP3 audio, TIF images,MPEG-4 video, PDF or any other suitable data format.

The exemplary header extension 762 can be of variable length andincludes a number of parameters that describe various attributesassociated with the content. Each parameter includes a one-byteParameter ID field and a variable length Body field. An exemplary listof parameters is shown in Table 3 below.

TABLE 3 Para- Length meter ID (bytes) Description 0 4 StartALFN:Specifies the time in ALFNs when the content is to be presented. If thisvalue is 0 or absent the content should be presented immediately. 1 4EndALFN: Specifies the time in ALFNs when the content is no longerpresented. If this value is 0 or absent the content should be presentedindefinitely until subsequent content is received. 2 1 Duration:Specifies the duration in ALFNs of content presentation. If this valueis 0 or absent the content should be presented indefinitely untilsubsequent content is received. 3 1 Block Offset: Specifies the blockoffsets of the start and end ALFNs. The first 4 bits represent the startoffset and the next 4 bits represent the end offset. 4 4 ContentID: Aunique ID to identify or correlate a particular piece of content. Thestructure of the ID is typically application specific. 5 4 Extended BodyLength: Indicates the body length in the number of bytes. Used inconjunction with a Body LEN of 0 in the header core.

As illustrated in Table 3, the header extension 762 can include startand end times, and durations for presenting content in the body 764.Additionally, the header extension can include a block offset thatallows the start and end content presentation times to be offset inincrements of 1/16 of the modem frame time (i.e., if the modem frametime is 1.48 seconds, then one block is 92.5 msecs in length). The blockoffset thereby allows fine-tuning of the synchronization of the datacontent with the audio to within approximately 92.5 msecs. Certainembodiments may provide a content reuse capability. For example, theextension header may include a Content ID descriptor that uniquelyidentifies the content described by the component. Receivers that havethe capability to store content can store the content referenced by theContent ID using the Content ID as an index. If in the future thereceiver identifies the same Content ID, instead of accessing thespecified RLS port to retrieve the content, the receiver can insteadretrieve the content from memory. This may be particularly advantageousfor content that is repetitive. For example, assume that a Top 40s radiostation broadcasts a limited number of songs. Therefore the receivercould store the album art associated with each of these songs and couldretrieve and display the album art as soon as each song begins.

In exemplary embodiments, data control instructions (e.g., SIG) areincluded in each modem frame that associate the data content from theclient 700 with the audio. These data control instructions cause thereceiver to read the appropriate RLS port to access data content that isto be rendered in synchronization with the audio. As discussed above,each modem frame typically includes a SIG. The SIG includes informationregarding the data and audio services that are advertised in SIS,including RLS port assignments. SIG allows the receiver to determinethat a service exists, pursue reception of the indicated service, andrender the service if it is selected. However, it should be noted thatSIG does not necessarily provide access to the contents of the service,for example, if the service is a CA service. SIG is broadcast over afixed RLS port by the radio station that provides the service and isperiodically updated.

Structurally, the SIG contains information pertaining to each servicebeing broadcast that is organized into service records. Typically, aseach client connects to the importer, a new audio or data service recordwill be constructed for that service. Service records typically includeinformation descriptors (i.e., attributes of the service). For example,an audio service record will typically include information thatdescribes the genre, additional processing instructions, and a servicedisplay name. In addition, a service may have other services associatedwith it. For example, an SPS may have data services associated with itas subservices that could include scrolling text, album art, closedcaptioning, product purchase information (e.g., ID3 tags), etc. In thiscase, the information about the associated subservice is included in theservice record of the main service. When a digital radio broadcastreceiver receives and decodes the SIG, it parses the information of theservice records to determine whether there are any associatedsubservices and renders any information about that subservice with thecurrent service. For example, if the receiver tunes to and renders SPS1,and the service record for SPS1 includes a subservice that includesalbum art, then the receiver will access the associated RLS portcontaining the album art.

An exemplary SIG message is illustrated in FIG. 14. The example in FIG.14 includes two concatenated service records, Service Record #1 andService Record #2. Service Record #1 describes an audio service (e.g.,SPS) and an associated data service. Service Record #1 includes a mainaudio service and a single associated data service, indicated by themain and subservice tags. The main service is an audio service andincludes audio service information descriptors. The subservice is anassociated data service (e.g., album art or closed captioninginformation) and includes data service information descriptors.Likewise, Service Record #2 describes only a main data service (e.g.,stock ticker or weather information). Service Record #2 includes a maindata service tag and data service information descriptors.

While the data content is described above as being associated with theaudio by including subservice information descriptors in the SIG, incertain embodiments the data content can be associated with the audio inother ways. For example, a descriptor of the main service could includea link to associate the audio service with a different data servicerecord.

After the digital radio broadcast transmitter broadcasts the modemframes over the air, a digital radio broadcast receiver then receivesthe modem frames and processes them so that the included content can berendered for an end user. Advantageously, a receiver may be able toreceive programming information regarding stations that broadcast onlyin legacy analog waveform and otherwise have no digital or other meansof conveying their program schedule.

An exemplary process of receiving, processing, and rendering the datacontent is described below. First, the user powers on the digital radiobroadcast receiver and then tunes the receiver to a desired radiostation. On power-up, the host controller 240, 296 begins to repeatedlyrequest various types of data (e.g., SIS, SIG, and LOT segments) fromthe baseband processor 201, 251. The baseband processor 201, 251retrieves the SIS and SIG from the modem frame, decodes them, andcommunicates them to the host controller 240, 296 responsive to arequest. The host controller 240, 296 then parses the SIG record of thecurrently selected service to determine whether the station isbroadcasting any associated data content. This indication will typicallyinclude either identifying a component associated with the audiocomponent or a descriptor associating the audio component with anotherdata service. If associated data content is available on a particularstation, the SIG will also indicate the RLS port number on which theassociated data content can be received.

In certain embodiments the host controller may cause the display controlunit 242, 298 to render an indication to the user that associated datais available. For example, in closed captioning implementations thiscould be in the form of a lighted “Closed Captioning Available” buttonor an icon on a GUI. In certain embodiments, the user may be able tochoose whether to activate the closed captioning at this point. The usercan then activate the closed captioning, e.g., by pressing a suitablebutton, which can be for example, either a physical button on thereceiver or a soft key button on a GUI. In certain embodiments, the hostcontroller may automatically begin rendering available data contentwithout requiring user input.

While the receiver is tuned to a particular radio station, the basebandprocessor 250, 251 is continuously receiving and buffering RLS packetsthat are broadcast from the radio station. In embodiments directed topacket-mode transmission using LOT protocol, the data processor 232, 288may also be reassembling the packets into objects. These objects arethen passed to the host controller 240, 296 responsive to a request(e.g. a polling event). Alternatively, RLS packets could be passed tothe host controller 240, 296, which could then reassemble them intoobjects. Additionally, in embodiments directed to byte-streaming datatransmission, the RLS packets could be reassembled in either the dataprocessor 232, 288 or the host controller 240, 296. Furthermore, thedata content can then be reconstructed based on the content protocoldescribed with reference to FIG. 13 above. For example, the data contentpackets can be distinguished and reassembled by utilizing the SYNC bytesof the header core 760. The receiver can determine the revision of thecontent protocol based on the PR fields to determine whether the contentprotocol is supported. Further, the header core 760 provides the typeand format of the data content so that it may call the appropriaterendering application.

The host controller 240, 296 then renders and/or stores the reassembleddata content. The process of rendering and/or storing the data contentmay vary depending on the specific implementation and the receivercapabilities. For example, closed captioning information is typicallyrendered immediately in synchronization with the audio (i.e., thesynchronization is performed by the digital radio broadcast transmitterand the receiver makes no determinations about the relative renderingtiming of the data content) and the data content is not stored.Similarly, radio karaoke and streaming text would also be immediatelyrendered and not stored. On the other hand, album art, image slideshows, and product purchase information will typically be stored forlater rendering in synchronization with the audio based on the timinginstructions included in the header extension of the content protocolpacket. In other words, the data content is synchronized with the audiobased on timing instructions inserted by the digital radio broadcasttransmitter. In certain embodiments that allow for content reuse, thestored album art, image slide shows, and product purchase informationcan be indexed with a Content ID no that it can be accessed multipletimes. The rendering applications can be coded in software using anysuitable programming language such as C, C++, or for example andimplementing such applications is within the purview of one of ordinaryskill in the art.

Additionally, different receivers will have different input, display,and memory capabilities. Some typical receiver's displays may include 4line by 16 character LED or LCD displays, 2 line by 16 character LED orLCD displays, 256 color OEL displays, multi-line back lit LCD displayswith 6″ or larger multimedia displays, and portable radio back lit LCDdisplays. Generally the receivers with more advanced displays have moreavailable memory. Simpler receivers may only have a small amount of RAM(e.g., less than 50 Kbytes) while more advanced receivers may have alarger amount of RAM (e.g., 100 Kbytes or more) as well as non-volatilememory such as Flash ROM (e.g., built-in Flash, a hard disk drive,and/or a SD® Memory Card). Advantageously, exemplary embodiments of thepresent disclosure provide adaptable rendering and storage based on thecapabilities of the receiver.

The data content may be stored in any suitable memory structure. Forexample, a file system could be used such as NTFS or Journaling FlashFile System version 2 (JFFS2). Alternatively, the files could be storedin a database such as SQLite or MySQL. Naturally, the memory structureutilized should be consistent with the memory capabilities of thereceiver. Thus more capable receivers could have more complex memorystructures. In some embodiments the data content may be stored innon-volatile memory. In these cases, the data content may be availableimmediately upon power-up without requiring the download of any new datacontent.

The way the data content is rendered may also depend on the receivercharacteristics (e.g., display or memory capabilities) and/or accordingto user choice. For example, a simple embedded receiver may only receiveand display simple text-based data content while a more capable receivermay display, for example, image slide shows, album art, and even video.Once the data content has been formatted for the display, it can then berendered by the DCU 242, 298. In some embodiments filtering data contentmay be performed according to the end user's choice. Advantageously, thedisplayed data content may be reduced, for example, by preventingdisplay of album art or closed captioning, upon the end user's selectionand irrespective of the display's further capabilities.

Exemplary applications for synchronizing data content with audio contentwill now be described. The examples include an album art/image slideshow/video application, a closed captioning application, a productpurchase information application, and a scrolling text application.However, it should be understood that these examples are provided forillustrative purposes only and should not be considered to limit thescope of the disclosure or the claims.

An album art, an image slide show, and a video application would alltypically operate in a similar manner. As described above with referenceto FIGS. 11 and 12, the exporter 20 sends a request message to theimporter 18 for a logical channel to generate a modem frame. Part ofthis request is the ALFN of the current modem frame. The importer 18then makes a content request to the client application 700, whichrequest includes the current ALFN and the time at which the audiotransmitted in the modem frame is expected to be rendered by a digitalradio broadcast receiver. In this case, the client application 700 maybe, for example, an album art and/or an image slide show applicationthat includes an image repository containing, for example, JPG or GIFimages. The client application 700 also may be a video applicationincluding, for example, an H.264 video encoder, and a video repositorycontaining, for example, MPEG-4 video clips. The client application 700typically also has access to information related to the audio content.

The client application 700 schedules the transmission of the relevantimage and/or video for transmission such that the image and/or video isavailable at the receiver prior to the anticipated rendering time of therelated song. The nature of the scheduling algorithm is animplementation consideration that would be within the purview of one ofordinary skill in the art. Any suitable scheduling technique could beused that would allow the images/videos to arrive at the receiver intime for rendering with the associated audio. In certain embodiments, asophisticated scheduler could allow the image and/or video to arrive atthe receiver just in time for it to be rendered with the associatedaudio.

For example, a scheduling application could schedule rendering of one ormore images/videos associated with a song or audio program (e.g.,advertisement, sporting event, talk show, etc.) based on the start/endtimes of the song or audio program (or equivalently start time and songduration) and a duration percentage for displaying the images/video(i.e., how long each image is to be displayed with reference to theduration of the song or audio event). To obtain the song start/endtimes, the application could have access to a database that includes anaudio service's play list, wherein the database includes songsassociated with the time when each song will be input into the importer18 or exporter 20 for broadcast. To obtain a duration percentage foreach image/video, the image/video repository could include a displayorder and information describing a predetermined percentage of theassociated song. The scheduler would determine the appropriate times forrendering the images/videos based on this information and include thesetimes with the transmitted image/video using, for example, the contentprotocol described above with reference to FIG. 13.

FIG. 15 illustrates an exemplary image scheduling application operation.In the example, two songs are scheduled to be played. An audio play listdatabase indicates that Song 1 is scheduled to be sent to the exporter20 at time T₁ and Song 2 is scheduled to be sent to the exporter 20 attime T₃. Song 1 has two associated album art images (e.g., a front albumcover and a back album cover), while Song 2 has only one album artimage. The front album cover of the album is supposed to display for thefirst 70% of Song 1 while the back album cover is supposed to displayfor the last 30%. Given T₁ and the difference between T_(C) and T_(A),the application determines the time, T_(Rx1), at which Song 1 will beginbeing rendered by a receiver (i.e., T_(Rx1)=T₁+(T_(A)−T_(C)), and thetime T_(Rx3) at which Song 2 will begin being rendered by a receiver(i.e., T_(Rx3)=T₃+(T_(A)−T_(C))). The application then schedulesrendering of the front album cover at T_(Rx1) and the back album coverat time T_(Rx3). Similarly, based on a duration percentage of 30%, theapplication determines the time T_(Rx2) to begin displaying the backalbum cover. The times T_(Rx1), T_(Rx2), and T_(Rx3) would then betransmitted with their respective album art images.

The images and/or videos are encoded using the content protocoldescribed above with reference to FIG. 13. Specifically, the header core760 would typically include timing instructions (e.g., StartALFN,EndALFN, duration, and/or block offset) that will cause the receiver torender the images/videos in synchronization with the audio. These timinginstructions are adjusted by adding the difference between the T_(A) andthe T_(C) to account for system latency, for example as described abovewith reference to FIG. 15. Additionally, the SIG record for the servicewould indicate that the receiver should use, for example, an album artor image slide show application to render the data content by includingMIME type identifiers such as application/x-hdradio-std/album-art(0x79a521f4) or application/x-hdradio-std/slide-show (0x065945d07). Theclient 700 sends the encoded images/videos to the importer 18. Theimporter 18 then sends them to the exporter 20 for digital radiobroadcast transmission. It should be noted that images and videos willtypically be encoded and transmitted using packet transmission (e.g.,LOT) but they may also be transmitted using byte-streaming. However, oneof skill in the art would appreciate that when images or videos aretransmitted via byte-streaming, available broadcast bandwidth may limitthe size of images/videos. For example, larger images and videostypically take longer to transmit assuming a fixed bandwidthavailability. Therefore, assuming that the images/videos are transmittedso that they arrive just in time for rendering at the receiver, thebandwidth constraints may limit the use of byte-streaming to images orvideos that can be broadcast within, for example, the duration of asong, so that the image/video is available for rendering at thebeginning of the next song.

In operation, the receiver will receive and download the images and/orvideos, which will typically include timing instructions in the headerif the packet transmission mode is being used. The receiver then pollsthe ALFN, which is broadcast in the SIS. When the timing instructionsindicate that the image or video should be displayed (e.g., the polledALFN matches the StartALFN of the stored image), the image/video will bedisplayed by the display control unit in synchronization with thereceiver rendering the audio via the audio speakers. In certainembodiments, if no images are available the receiver can display adefault image.

A closed captioning application would provide text information that issynchronized with the audio. Examples of such an application can includeradio for the hearing impaired or language translations. In this case,the client application 700 is a closed captioning application. Forexample, the client 700 could receive closed captioning input from ahuman operator, a software implemented speech-to-text translator, or apre-stored text file containing the text of the speech that hasassociated rendering times for components of the speech. For a humanoperator, the client could present a word processing screen to theoperator that presents the text that has been typed and indicating whichtext has already been transmitted. For example, the words that have beentransmitted could be grayed out after they have been sent based on thecontent request messages received from the importer 18.

The text would be encoded using the content protocol described abovewith reference to FIG. 13. Specifically, the header core 760 wouldinclude SYNC bits that allow the receiver to reassemble the text packetsas described above. The text packets can be delivered, for example,using a fixed time or a number of characters to delimit the packets. Theheader extension 762 may also include information indicating that thetext should be rendered by the receiver as soon as it is received.However, in certain embodiments the header core 760 can include timinginstructions (e.g., StartALFN, EndALFN, duration, and/or block offset)that will cause the receiver to render the text in synchronization withthe audio. These timing instructions are adjusted based on T_(A), T_(D),and T_(C) to account for system latency. Additionally, the header core760 would indicate that the receiver should use a text renderingapplication to render the data content by including MIME typeidentifiers such as application/x-hdradio-std/closed-caption(0x08c805636).

Typically, the client 700 sends the text packets to the importer 18 sothat they arrive at the receiver just in time to be rendered insynchronization with the associated audio. Accordingly, this applicationwould typically use byte-streaming to minimize delivery jitter.Additionally, in certain embodiments the I2E link delay may be reducedto minimize latency. In certain embodiments, the text packets can bebuffered by the client 700 to account for system latency. For example,the client 700 can use T_(A), T_(D), and T_(C) to determine how much tobuffer the text packets so that the text is rendered in synchronizationwith the audio. In certain embodiments, the client 700 can also useT_(A), T_(D), and T_(C) to buffer the audio by providing an input to theaudio encoder, such that there is sufficient time for the text to begenerated and delivered to the importer 18.

In operation, the receiver may receive and immediately render the textcharacters. Alternatively, the text can be rendered in synchronizationwith the audio based on timing instructions as described above. Thedisplay can be updated periodically as text is received (e.g., reset orlines of text scrolled up or down in a text box). For example, thereceiver could establish an average number of words per minute orcharacters per second so that the words would be rendered smoothly tomitigate the burstiness of delivery. Additionally, the display could beupdated upon receipt of a new content packet, after a predeterminedamount of time, or when the text box on the display is full.

A radio karaoke application would also provide highly synchronized textwith the audio and would operate very similarly to the exemplary closedcaptioning application described above. However, in certain embodimentsa radio karaoke implementation may also include a receiver capabilityfor reducing and/or eliminating the vocals from an audio track in realtime. This may be desirable to improve the karaoke experience for users.FIGS. 16 a and 16 b illustrate exemplary components for receivercomponents in accordance with certain embodiments. FIG. 16 a illustratesan exemplary digital technique for reducing and/or eliminating the vocalcomponents of an audio track. With reference to FIGS. 7 and 8, theprocessor 224, 280 and blocks 230, 284 of an exemplary digital radiobroadcast receiver are shown. The audio signal from blocks 230, 284enters the vocal eliminator and audio processing block 770 where it isprocessed. The vocal eliminator and audio processing block 770 can beimplemented, for example, in the baseband processor 201, 251 or in aseparate processing system that includes software, hardware, or anysuitable combination thereof; and performs digital signal processingoperations on the audio sufficient to substantially filter out the vocalcomponent.

Any suitable vocal elimination algorithm could be used as would be knownto one of skill in the art. For example, assuming that the vocals areencoded on a center channel an exemplary algorithm might be as follows.The processing system could transform the left and right channels of theaudio signal to the frequency domain using, for example, the FastFourier Transform (FFT) or Fast Hartley Transform (FHT). Then, for eachfrequency component, where L is the 2D vector from the left channel, andR is the 2D vector from the right channel, the processing system wouldcompute the center component C=L/|L|+R/|R| and then compute α such that(L−αC)·(R−αC)=0. Essentially, the processing system would scale C sothat when it is subtracted from L and R, the two resultant vectors areperpendicular. Expanding this gives the equation(C·C)α²−C·(L+R)α+(L·R)=0, which the processing system may solve for α,for example, by the quadratic formula. Then, it would compute C′=αC,L′=L−αC, and R′=R−αC. Finally, it would transform L′, R′, and C′ back totime domain using an inverse FFT or FHT, overlap and add the signalcomponents back together. While this exemplary algorithm may result inan undesirable removal of low frequency components, a low pass filtercould also be used to extract and then reinsert these low frequencycomponents after the center component has been removed.

The vocal eliminator and audio processing block 770 also includes acontrol signal input that may, among other functions, activate anddeactivate the vocal eliminator operation. This control signal may begenerated by the host controller 240, 296 according to a user's input.For example, if a user is using a radio karaoke application, the usermay be presented with an icon or menu selection that allows them tochoose to eliminate the vocals (e.g., a “VOCAL ELIMINATOR” button).After processing the audio signal is then output to a digital-to-analogconverter 772 (DAC), which converts the digital signal to an analogaudio output suitable for rendering by, for example, analog speakers.

FIG. 16 b illustrates an exemplary analog technique for reducing and/oreliminating the vocal components of an audio track. The analog techniqueis similar to the digital technique except that the vocal eliminator andaudio processing block 774 is implemented after the DAC 772 andtypically would use electronic components such as, for example, adifferential amplifier for reducing the vocals and a low pass filter formaintaining the low frequency components.

In certain embodiments, the receiver may also provide the capability forrecording and storing a user's karaoke performance. For example, in areceiver including a microphone input and sufficient data storage (e.g.,a hard disk drive, flash ROM, and/or removable memory storage such as anSD card), a karaoke application at the receiver could allow a user toactivate a recording function. Once the recording function is activated,the user's vocals and the audio track, with or without the vocalsfiltered, could be mixed and stored in memory. The mixed audio could bestored, for example, in HDC compressed format and could be replayed at alater time. Exemplary storing and replaying functions in digital radiobroadcast receivers are disclosed in U.S. patent application Ser. No.11/644,083 (U.S. Patent Pub. No. 2008/0152039), which is incorporated byreference herein in its entirety.

A product purchase information application could send ID3 based (UFID)product codes that are associated with songs that will be renderedbefore the actual content is broadcast. This application would be verysimilar to the album art and image slide show applications describedabove but there are a few differences. First, the type and size of thecontent is different (i.e. ID3 tags instead of images). Therefore, sinceID3 tags are not very large, each product code can be broadcast in asingle content protocol packet and thus they may more readily be sentusing byte-streaming. Also, the SIG record for the service wouldindicate that the receiver should use a product purchase informationapplication to render the data content by including MIME typeidentifiers such as application/x-hdradio-std/product-info (0x1343c25).Further, the client 700 would use the rendering start and stop times asvalidity times to match the product purchase information with thespecific content being rendered. On the receiver side, once the user ofthe receiver inputs instructions to purchase a product associated withthe current media content (e.g., presses a tagging button), theapplication can poll the current ALFN from the SIS and match this ALFNto the proper product information. This product purchase information canthen be transmitted to a content provider to consummate a sale. Adetailed example of tagging for digital radio broadcast receivers can befound in U.S. Patent App. Pub. No. 2009/0061763, which is incorporatedby reference herein in its entirety. Client applications for sending PSDinformation (typically ID3 tags) associated with the audio could operatein a similar manner.

Finally, a scrolling text application is an informational textapplication wherein the text is not as tightly coupled to the audio asin the closed captioning application. Examples of scrolling textapplications can include stock quotes, traffic advisories, etc. Theoperation of a scrolling text application is almost identical to that ofa closed captioning application. However, timing instructions need notbe provided and the level of synchronization between the audio and thetext packets need not be very high. For example, there would be littleneed to buffer the audio to account for text generation time or toreduce the I2E link delay time. Also, the header core 760 would indicatethat the receiver should use a scrolling text application to render thedata content by including MIME type identifiers such asapplication/x-hdradio-std/scrolling-text (0x97f54d9b). Also, the contentpacket header extension 762 may be sent with a duration indicator sothat the receiver can determine a proper scrolling rate. In certainembodiments, if no new text packets are available at the receiver, thenthe receiver will scroll the last text packet until anew one isreceived.

FIG. 17 a illustrates an exemplary process of encoding and transmittinga first media content (e.g., audio) and a second media content (e.g.,data content) in a digital radio broadcast system comprising aprocessing system, such that the second media content can be rendered insynchronization with the first media content by a digital radiobroadcast receiver. In step 800, the importer 18 determines a firstvalue (T_(C)) corresponding to a time at which a frame is to betransmitted by a digital radio broadcast transmitter.

In step 802, the importer 18 determines a second value (T_(A))corresponding to a time at which a first media content transmitted inthe frame is to be rendered by a digital radio broadcast receiver basedon a first latency, wherein the first media content is processed througha first signal path through the digital radio broadcast transmitter andthe digital radio broadcast receiver thereby incurring a first latencythat is based on an estimated time for processing the first mediacontent through the first signal path. For example, referring to FIG.11, main audio is output from the main audio source 714 to the audioencoder 716 in the exporter 20 and then to multiplexer 712. In contrast,secondary audio is output from the secondary audio source 702 to theaudio encoder 706, then through multiplexer 708 and finally to theexporter multiplexer 712 via I2E interface 710. Accordingly, it shouldbe clear from this example that main audio and secondary audio wouldtypically incur different latencies through the transmitter side.

In step 804, the importer determines a third value (T_(D)) correspondingto a time at which a second media content in the frame would be renderedby the digital radio broadcast receiver based on a second latency,wherein the second media content is processed through a second signalpath through the digital radio broadcast transmitter and the digitalradio broadcast receiver thereby incurring the second latency that isbased on an estimated time for processing the first media contentthrough the first signal path. This second latency is typicallydifferent than the first latency. For example, referring again to FIG.11, data content is output from the client 700 to the RLS encoder 704,then through multiplexer 708 and finally to the exporter multiplexer 712via I2E interface 710. Thus it should be apparent that the latency ofdata content will typically be different than the latency of audiothrough the transmitter side.

In step 806, the importer 18 communicates the first, second, and thirdvalues to a client application 700 via an API. The client application700 may be, for example, a closed captioning application, a karaokeradio application, a scrolling text application, album art, or a productpurchase information application. The client application 700 thenprocesses the second media content at a time determined by the clientbased on the first, second, and third values, thereby controlling thetiming at which second media content is to be transmitted, so as tosynchronize the timing of rendering the second media content at adigital radio broadcast receiver relative to the timing of rendering thefirst media content at the digital radio broadcast receiver. In step808, the importer 18 receives second media content for the frame fromthe client 700. Finally, in step 810 the importer 18 communicates thesecond media content to the exporter 20, which in turn generates theframe and communicates the frame to a digital radio broadcasttransmitter site via STL link 14. The generated frame includes the firstvalue, first media content, second media content, and data controlinstructions associating the second media content with the first mediacontent (e.g., SIG).

In certain embodiments, the first latency and the second latency aretransmission-location dependent meaning that the latencies can vary fromradio station to radio station and from one service to another. Incertain embodiments, the digital radio broadcast receiver renders thefirst media content and second media content without makingdeterminations about the relative rendering timing for the second mediacontent and the first media content. In certain embodiments, the framedoes not include an independent clock signal for synchronizing the firstand second media content.

FIG. 17 b illustrates an exemplary process of encoding and transmittinga first media content and a second media content in a digital radiobroadcast system comprising a processing system, such that the secondmedia content can be rendered in synchronization with the first mediacontent by a digital radio broadcast receiver. In step 820, the importer18 determines a first value (T_(C)) corresponding to a time at which aframe is to be transmitted by a digital radio broadcast transmitter. Instep 822, the importer 18 determines a second value (T_(A))corresponding to a time at which a first media content transmitted inthe frame is to be rendered by a digital radio broadcast receiver basedon a first latency, wherein the first media content is processed througha first signal path through the digital radio broadcast transmitter andthe digital radio broadcast receiver thereby incurring the firstlatency. In step 824 the importer 18 communicates the first and secondvalues to a client application 700 via an API. The client application700 may be, for example, a closed captioning application, a karaokeradio application, a scrolling text application, a product purchaseinformation application, an album art application, or an image slideshow application.

The client application 700 then processes the second media content basedon the first and second values to generate timing instructions that areincluded in a content protocol packet. The timing instructions areprovided so as to synchronize the timing of rendering the second mediacontent at a digital radio broadcast receiver relative to the timing ofrendering the first media content at the digital radio broadcastreceiver. In step 826, the importer 18 receives from the client 700second media content and the timing instructions for the digital radiobroadcast receiver to render the second media content at a predeterminedtime in synchronization with the first media content based on the firstand second values. In step 828 the importer 18 communicates the secondmedia content to the exporter 20, which in turn generates a frame andcommunicates the frame to a digital radio broadcast transmitter site viaSTL link 14. The generated frame includes the first value, second mediacontent, timing instructions (e.g., in the content protocol packetattached to the second media content), and data control instructionsassociating the second media content with the first media content (e.g.,SIG). This first frame is broadcast in sufficient time so that thesecond media content is available for rendering at the receiver in timefor it to be rendered in synchronization with the first media contentwhen it arrives. Finally, in step 830 the importer 18 communicates thefirst media content to the exporter 20, which in turn generates a secondframe and communicates the frame to a digital radio broadcasttransmitter site via STL link 14. The generated frame includes the firstmedia content.

FIG. 18 illustrates an exemplary process of receiving and rendering afirst media content in synchronization with a second media content in adigital radio broadcast receiver. In step 840, the baseband processor201, 251 receives a frame having first media content (e.g., audio),second media content (e.g., data content), and data control instructions(e.g., SIG) associating the second media content with the first mediacontent, wherein the second media content has been composed forrendering in synchronization with the first media content based on anestimated latency through the digital radio broadcast transmitter andthe digital radio broadcast receiver as discussed above.

In step 842 the baseband processor 201, 251 processes the first mediacontent through a first signal path in the digital radio broadcastreceiver, thereby incurring a first latency. For example, as describedabove with reference to FIG. 7, a digital demodulator 216 demodulatesthe digitally modulated portion of an incoming baseband signal. Thedigital signal is then deinterleaved by a deinterleaver 218, and decodedby a Viterbi decoder 220. A service demultiplexer 222 separates main andsupplemental program signals from data signals. A processor 224processes the program signals to produce a digital audio signal on line226. In step 844 the baseband processor 201, 251 also processes thesecond media content through a second signal path in the digital radiobroadcast receiver, thereby incurring a second latency that is differentthan the first latency. For example, referring to FIG. 7, data contentis processed as described above until the digital signal reaches theservice demultiplexer 222. The service demultiplexer 222 outputs datasignals to a data processor 232, which processes the data signals andproduces data output signals on lines 234, 236 and 238. The dataprocessor 232 then sends the data output signals (e.g., the second mediacontent) to the host controller 240 responsive to a polling request.Since the audio and the data content are processed through differentsignal paths in the receiver, the latencies of the audio and datacontent are typically different through the digital radio broadcastreceiver. Specifically, with reference to the above example the audio isprocessed by processor 224 and the data content is processed by dataprocessor 232 and then by the host controller 240, 296.

In step 846 the host controller 240, 296 then associates the secondmedia content with the first media content based on the data controlinstructions. For example, a SIG audio service record may includesubservice information descriptors that the host controller 240, 296uses to associate the audio with data content. In step 848, the hostcontroller 240, 296 renders the second media content in synchronizationwith the first media content based on the data control serviceinstructions, wherein the digital radio broadcast receiver renders thefirst media content and second media content without makingdeterminations about the relative rendering timing for the second mediacontent and the first media content. In certain embodiments, the framedoes not include an independent clock signal for synchronizing the firstand second media content. The second media content may include, forexample, closed captioning information, song lyrics, album art, imageslide shows, product purchase information, or scrolling text. In certainembodiments the second media content can be radio karaoke information(e.g., song lyrics) and the receiver can filter vocal components of theaudio in real time so as to reduce the vocal component as describedabove with reference to FIGS. 16 a and 16 b.

The previously described embodiments of the present disclosure have manyadvantages, including:

One advantage is that in certain embodiments, audio and data content canbe rendered in synchronization at the receiver without transmitting anindependent clock reference to the receiver that could be referenced forboth audio and data rendering. Thus there are no significantmodifications to the baseband processor required. Additionally,including an additional clock signal would require additional bandwidth,which is at a premium in digital radio broadcast systems.

Another advantage is that in certain embodiments, audio and data contentcan be rendered in synchronization at the receiver without referencingthe rendering of data content to the playback of the audio. Thus nosignificant changes to the baseband processor would be required.

The exemplary approaches described may be carried out using any suitablecombinations of software, firmware and hardware and are not limited toany particular combinations of such. Computer program instructions forimplementing the exemplary approaches described herein may be embodiedon a computer-readable storage medium, such as a magnetic disk or othermagnetic memory, an optical disk (e.g., DVD) or other optical memory,RAM, ROM, or any other suitable memory such as Flash memory, memorycards, etc. Additionally, the disclosure has been described withreference to particular embodiments. However, it will be readilyapparent to those skilled in the art that it is possible to embody thedisclosure in specific forms other than those of the embodimentsdescribed above. The embodiments are merely illustrative and should notbe considered restrictive. The scope of the disclosure is given by theappended claims, rather than the preceding description, and allvariations and equivalents which fall within the range of the claims areintended to be embraced therein.

What is claimed is:
 1. A digital radio broadcast receiver configured toreceive and render first media content in synchronization with secondmedia content, comprising: a processing system; and a memory coupled tothe processing system, wherein the processing system is configured toexecute steps comprising: receiving a frame having first media content,second media content, and data control instructions associating thefirst media content with the second media content, wherein the secondmedia content has been processed for rendering in synchronization withthe first media content based on an estimated latency through a digitalradio broadcast transmitter and a digital radio broadcast receiver;processing the first media content through a first signal path in thedigital radio broadcast receiver, thereby incurring a first latency;processing the second media content through a second signal path in thedigital radio broadcast receiver, thereby incurring a second latencythat is different than the first latency; associating the second mediacontent with the first media content based on the data controlinstructions; and rendering the second media content in synchronizationwith the first media content, wherein the digital radio broadcastreceiver renders the first media content and the second media contentwithout making determinations about relative timing of rendering thesecond media content and the first media content.
 2. The digital radiobroadcast receiver of claim 1 wherein the frame does not include anindependent clock signal for synchronizing the first and second mediacontent.
 3. The digital radio broadcast receiver of claim 1 wherein thefirst media content is audio.
 4. The digital radio broadcast receiver ofclaim 1 wherein the second media content is radio karaoke information,further comprising the step of filtering a vocal component of the audioin real time so as to reduce the vocal component.
 5. The digital radiobroadcast receiver of claim 1 wherein the second media content comprisesclosed captioning information.
 6. The digital radio broadcast receiverof claim 1 wherein the second media content comprises images.
 7. Acomputer-implemented method of receiving and rendering a first mediacontent in synchronization with a second media content in a digitalradio broadcast receiver, the method comprising: receiving a framehaving first media content, second media content, and data controlinstructions associating the first media content with the second mediacontent, wherein the second media content has been processed forrendering in synchronization with the first media content based on anestimated latency through a digital radio broadcast transmitter and adigital radio broadcast receiver; processing the first media contentthrough a first signal path in the digital radio broadcast receiver,thereby incurring a first latency; processing the second media contentthrough a second signal path in the digital radio broadcast receiver,thereby incurring a second latency that is different than the firstlatency; associating the second media content with the first mediacontent based on the data control instructions; and rendering the secondmedia content in synchronization with the first media content, whereinthe digital radio broadcast receiver renders the first media content andthe second media content without making determinations about relativetiming of rendering the second media content and the first mediacontent.
 8. The method of claim 7 wherein the frame does not include anindependent clock signal for synchronizing the first and second mediacontent.
 9. The method of claim 7 wherein the first media content isaudio.
 10. The method of claim 7 wherein the second media content isradio karaoke information, further comprising the step of filtering avocal component of the audio in real time so as to reduce the vocalcomponent.
 11. The method of claim 7 wherein the second media contentcomprises closed captioning information.
 12. The method of claim 7wherein the second media content comprises images.
 13. An article ofmanufacture comprising a non-transitory computer readable storage mediumhaving computer program instructions for receiving and rendering a firstmedia content in synchronization with a second media content in adigital radio broadcast receiver, said instructions when executedadapted to cause a processing system to execute steps comprising:receiving a frame having first media content, second media content, anddata control instructions associating the first media content with thesecond media content, wherein the second media content has beenprocessed for rendering in synchronization with the first media contentbased on an estimated latency through a digital radio broadcasttransmitter and a digital radio broadcast receiver; processing the firstmedia content through a first signal path in the digital radio broadcastreceiver, thereby incurring a first latency; processing the second mediacontent through a second signal path in the digital radio broadcastreceiver, thereby incurring a second latency that is different than thefirst latency; associating the second media content with the first mediacontent based on the data control instructions; and rendering the secondmedia content in synchronization with the first media content, whereinthe digital radio broadcast receiver renders the first media content andthe second media content without making determinations about relativetiming of rendering the second media content and the first mediacontent.
 14. The non-transitory computer readable storage medium ofclaim 13 wherein the frame does not include an independent clock signalfor synchronizing the first and second media content.
 15. Thenon-transitory computer readable storage medium of claim 13 wherein thefirst media content is audio.
 16. The non-transitory computer readablestorage medium of claim 13 wherein the second media content is radiokaraoke information, and wherein the steps further include filtering avocal component of the audio in real time so as to reduce the vocalcomponent.
 17. The non-transitory computer readable storage medium ofclaim 13 wherein the second media content comprises closed captioninginformation.
 18. The non-transitory computer readable storage medium ofclaim 13 wherein the second media content comprises images.